1. Field of the Invention
The present invention is generally related to an outboard motor and, more particularly, to an outboard motor that utilizes two independent and isolated air management systems to provide cooling air that flows over the engine and other heat emitting components and independently direct a stream of air into an air intake manifold of the engine.
2. Description of the Related Art
Many types of marine propulsion systems use air for two distinctly different purposes. One purpose is to satisfy the basic requirement of the engine which ingests air for the purpose of supporting combustion within its cylinders. The other purpose is to remove heat from various heat generating components, such as the engine itself, the alternator, and other devices of the marine propulsion unit. The air management systems known to those skilled in the art sometimes direct cooling air into the cylinders of the engine after it has removed heat from the heat emitting components. Some air management systems use multiple air streams to satisfy these various purposes and cause the air to slow along predefined paths that sometimes cause the various air streams to mix and sometimes segregate them.
U.S. Pat. No. 5,176,551, which issued to Blanchard et al. on Jan. 5, 1993, describes an arrangement for supplying combustion air to an outboard motor. The apparatus comprises a boat including a wall extending generally in the fore and aft direction and having therein an air outlet opening, a propulsion unit mounted on the boat and including a propeller shaft, an engine drivingly connected to the propeller shaft, and a cover surrounding the engine and having therein an air inlet opening, and a duct communicating between the air outlet opening and the air inlet opening.
U.S. Pat. No. 5,445,547, which issued to Furukawa on Aug. 29, 1995, describes an outboard motor having an engine compartment covered by an engine cover at its top portion and having an engine disposed within the engine compartment with its crankshaft directed in a vertical direction. Charging efficiency of the engine is improved with a simple structure and a shielding property of the entire surrounding of the engine is also enhanced. A suction chamber communicating with an intake section of the engine is disposed on a surface other than the top surface of the engine and on one side of the inside of the engine compartment, an air intake port is provided in the engine cover at a position close to the other side of the inside of the engine compartment, an air exhaust port is provided in the engine cover, and a duct is provided within the engine compartment for leading air from the air intake port towards the suction chamber while making a detour to avoid a route above the engine.
U.S. Pat. No. 5,713,772, which issued to Takahashi et al. on Feb. 3, 1998, describes a cooling arrangement for an outboard motor. A number of embodiments of four cycle internal combustion engines have belt driven overhead cam shafts. The power head of the outboard motor includes a protective cowling that has an atmospheric air inlet and the air drawn through this atmospheric air inlet is directed over a timing belt that drives the cam shaft from the engine crankshaft for its cooling.
U.S. Pat. No. 5,899,778, which issued to Hiraoka et al. on May 4, 1999, describes an outboard motor induction system. The system for an outboard motor includes a cover extending over a top end of the engine. The cover defines an air duct leading from an intake chamber defined by the cowling to an intake pipe of the air intake system of the engine. The cover also defines an air duct in communication with the engine compartment and leading to an exhaust chamber defined by the cowling.
U.S. Pat. No. 5,937,818, which issued to Kawai et al. on Aug. 17, 1999, describes a ventilation system for an outboard motor. It has a water propulsion device and an internal combustion engine positioned in a cowling. The engine has an output shaft arranged to drive the water propulsion device. The ventilating system includes an air inlet in the cowling which permits air to flow into an engine compartment in which the engine is positioned. An exhaust port is to positioned in the cowling. The system also includes a mechanism for drawing air through the inlet into the compartment and expelling air out of the compartment through the exhaust port after the engine has stopped.
U.S. Pat. No. 5,992,368, which issued to Okamoto on Nov. 30, 1999, describes an induction system for an outboard motor. It has a cowling and a water propulsion device and the engine is positioned in the cowling and has an output shaft arranged to drive the water propulsion device. The engine has at least one combustion chamber and the induction system is arranged to provide air to each combustion chamber.
U.S. Pat. No. 6,132,273, which issued to Nakayama et al. on Oct. 17, 2000, describes a cowling for an outboard motor. It provides atmospheric air to the engine of an outboard motor for engine cooling and combustion while inhibiting water intake. The protective cowling incorporates one or more inlets, an air chamber, and ducts of different sizes for permitting atmospheric air to enter the engine compartment.
U.S. Pat. No. 6,183,323, which issued to Tanaka et al. on Feb. 6, 2001, describes an outboard marine drive powered by an air cooled internal combustion engine. The engine is received in an under case and is closed by both a fan cover and an engine cover so that the engine may be entirely covered by the engine cover jointly with the under case for a favorable aesthetic effect. However, the fan cover covers the engine closely in cooperation with the under case so that a narrow air passage is defined around the engine, and cooling air of high velocity can be continuously passed around the engine.
U.S. Pat. No. 6,413,131, which issued to Phillips et al. on Jul. 2, 2002, discloses an air flow system for an outboard motor. An outboard motor is provided with an air duct located within the cavity of a cowl of an outboard motor. The air duct defines a chamber within it in association with first and second openings that allow heated air to flow, through the creation of convection currents, out of the engine compartment under a cowl. This convection removes heat from the fuel system components and reduces the likelihood that vapor lock will occur subsequent to the use of the internal combustion engine that is followed by turning the engine off.
U.S. Pat. No. 6,623,319, which issued to Isogawa on Sep. 23, 2003, describes a cowling and ventilation system for an outboard motor. It includes a cowling substantially enclosing an engine therein. The engine has an air induction device for introducing air to a combustion chamber and an exhaust system for communicating exhaust products away from the combustion chamber. The air induction device has an intake opening near a front end of the engine. The cowling has an air inlet at a rear portion of the cowling. An air guide member is disposed between the cowling air inlet and an engine cover which is positioned atop the engine. The air guide member and engine cover cooperate to direct air toward a rear and center of the engine.
U.S. Pat. No. 6,899,579, which issued to Bruestle on May 31, 2005, discloses a marine propulsion device with variable air intake system. An air flow control mechanism is provided to control the flow of air through an opening formed in a portion of a cowl of an outboard motor. The air flow control mechanism is configured to be movable between a first position and a second position to affect the magnitude of air flowing through an air passage defined as being the space between the opening formed in the cowl and an exit through which the air can leave the cavity of the cowl. The air flow control mechanism can control the flow of air as a function of an operating characteristic of the engine, such as its operating speed, the load on the engine, or the operating temperature of the engine.
U.S. Pat. No. 7,021,262, which issued to Belter et al. on Apr. 4, 2006, discloses an undercowl plenum chamber with preferential air paths. An air intake system for an outboard motor provides parallel air flow paths between an opening formed in a cowl of the outboard motor and an air intake manifold of an engine under the cowl. A first air path flows in a relatively direct path between the opening in the cowl and the first inlet of a plenum chamber. A second air flow flows in a less direct path from the opening in the cowl to a second inlet of the plenum chamber. The second air flow is used to remove heat from a preselected component, such as an alternator, before it rejoins the first air flow within the cavity of the plenum chamber and is directed, in combination with the first air flow, through an intake air conduit connected to an outlet of the plenum chamber and to an air intake manifold of the engine.
U.S. Pat. No. 7,238,068, which issued to Nagashima et al. on Jul. 3, 2007, describes a boat and outboard motor having an air intake system. The boat includes an outboard motor having an internal combustion engine enclosed within a cowling. The cowling has a rear inlet port for allowing outside air to be drawn into the cowling. A closure member selectively closed the inlet port depending upon certain engine operating parameters. In another embodiment, the cowling also includes a front air inlet port, and a front closure device for selectively opening and closing the front inlet port.
U.S. Pat. No. 7,299,783, which issued to Broman et al. on Nov. 27, 2007, discloses an auxiliary control of air flow through an engine enclosure of an outboard motor. A marine propulsion device is provided with an air control system that draws air from a region under the cowl of the outboard motor and induces a flow of air out of the region. The air is caused to flow through a second opening formed in the cowl. As a result, air drawn into the cowl through a first opening can flow either into the engine through its throttle body mechanism or out of the space under the cowl, as induced by the operation of the fan.
U.S. Pat. No. 7,401,598, which issued to Ochiai on Jul. 22, 2008, describes an outboard motor with forward air intake and air-cooled fuel pump. An outboard motor can comprise a cowling for covering an engine, a high pressure fuel supply system, and a low pressure fuel supply system. The high pressure fuel supply system can have a vapor separator tank and a high pressure fuel pump. The low pressure fuel supply system can have a low pressure fuel pump. A heat insulating chamber, defined from a space for accommodating the engine, can be formed within the cowling. The heat insulating chamber houses the low pressure fuel pump in the fuel filter.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
As illustrated by the patents described above, those skilled in the art of marine propulsion devices are aware of many different techniques and systems that manage the air flow under the cowl of the marine propulsion device. Some systems provide an air inlet through a cowl wall which allows a stream of air to flow in thermal communication with an engine and other associated heat emitting components located under the cowl. That air can be directed to a throttle body of the engine and ingested for use in the combustion process within the engine. Some of the air can be directed through an air outlet opening in the cowl to remove heat from the internal cavity within the cowl. Fans have been used for the purpose of inducing the air flow within the cavity of the cowl. Of the many air management systems and methods for drawing air into the cavity of a cowl, ingesting air into the air intake manifold and cylinders of an engine, directing a flow of air over heat emitting components located under the cowl, and causing air to exit from the cavity under the cowl through an opening formed in the wall of the cowl, no known systems provide two completely isolated and segregated air streams which independently provide air for combustion within the engine and provide air in a cooling stream to remove heat from the engine and other components without mixing the two air streams. Since the purposes of an air induction system for an engine and an air cooling system for the engine are often mutually exclusive, it would be significantly beneficial if a marine propulsion device could be provided with two completely independent air streams that provide an air induction stream and a component cooling stream that do not interact.